A crane is widely used to transport a load. An operator of a crane must be skilled in its operation to frequently and repeatedly turn the operation switch of the crane on and off so as to suppress the sway of the load during its transfer by the crane. Moreover, since the operator has to wait so as to perform the next step until the sway stops once it is generated, some problems in the safety aspect, such as a problem in that a load is being made unstable and so on, are occasionally caused. Therefore, suppressing the sway of the load of a crane is a great subject in the crane industry.
Therefore, various improvements have been developed for suppressing the sway of the load of a crane. For instance, JP A 2000-38286 discloses a sway-suppressing device for a rotary crane. The device includes: monitor means for imaging the position of a transported load; image processing means for processing the output on the image from the monitor means to compute information, including information on the distance of the load; angle detecting means for inputting the output of the image processing means to detect the angle of a crane boom; and crane driving means for controlling the operation of the crane boom according to the information on the distance from the image processing means and the information on the crane boom angle from the angle detecting means so that the transportation orbit of the load, which orbit is drawn by hoisting, drawing inward, and turning the crane boom, is made to form straight lines in the form of a polygon.
However, clearly from the teaching of JP, A, 2000-38286, the conventional improvement for the sway suppression requires the monitor means, the angle detecting means, etc., and the arrangement for them is complicated.